Stethoscopes and like apparatus have been used for many years to listen to sounds made by the human body and to make diagnostic analysis of various conditions in the human body. The sounds produced are typically in the sonic range and while stethoscopes are, obviously, widely used by the medical profession, the types of analysis and uses for such apparatus is relatively limited primarily to the chest cavity area (e.g., breathing and gas flow in the lungs, etc.) and for blood pressure readings in the cardiovascular system.
My patent application Ser. No. 07/569,121 discloses a non-invasive diagnostic apparatus and method wherein the human body or a portion thereof is placed in a body of an acoustically transmissive fluid, such body of acoustically transmitting fluid being contained in a container preferably having sidewalls formed of or coated with acoustically absorbent material. One or more hydrophones are located in the body of fluid to detect or "listen" to sounds, such as cardiovascular sounds, gas flow and skeletal sounds made by body movements. These sounds are passed through a preamplifier, a bandpass filter and discriminator, the function of which may be performed by microprocessors, to a recorder and/or display device. The recorder can record body sounds much in the fashion of an strip chart recorder used for EKG and/or EEG. Typical pool water with chlorine, or salt water, or oils, such as vegetable oils can be used for the acoustically transmissive medium. In addition to audible sounds, the method and apparatus are particularly useful for listening to infrasonic or subsonic sounds. The subject is placed or immersed in the body of acoustically transmissive liquid in a container having acoustically absorbing walls so that there are no unwanted reflections of sounds launched in the water from the human body reflecting off of the walls. One or more hydrophones located in the body of water are used to detect the sonic energy launched by the human body. The human in the body of acoustic liquid is instructed to go through a particular sequence of movement, for example, the arms, (flexion, extension, abduction, adduction), or the back, or legs (inversion eversion), etc. and record is made of the sounds emitted during each of the movements of the specific body parts or the specific movement made by a given patient. For example, an athlete may be asked to bend his or her knee (flexion, extension), elbow (flexion, extension) and the like and a record is made of the sounds generated and launched into the acoustically transmissive liquid. Similar recordings are made for a large number of individuals to provide a norm of the movements of a particular body part in a particular direction and/or at a particular rate of speed. These records then form a database which may be stored in the computer database and used to detect departures from the normal sounds made and thereby provide the physician with a greater body of knowledge to enable successful treatment for the patient.
As noted above, the human acoustic signature is comprised of three main sound groups: Respiratory, Cardiovascular and Musculo-skeletal. When these sounds are analyzed in a liquid medium (e.g., seawater or lake or river water), shared by other living creatures like fish, mollusks, small mammals, crustaceans, etc., any respiratory sound analysis is affected by a large variety of extraneous sounds, such as fish swimming bladders and other hissing sounds. In addition, any musculo-skeletal sounds are diminished significantly if the subject diver is not moving or is moving extremely slowly.
However, the human cardiovascular system signature is strong. It is involuntary and cannot be suppressed, and is easily distinguished from sounds produced by any sea creatures, even sea mammals and fish.
The invention detects the presence, direction and proximity of a human being in or under water regardless of the type of breathing apparatus or swimming method. And, after comparing the incoming signal with the sonic profile of human cardiovascular sound, recorded digitally on the ROM, it can proceed to sound a warning to alert the operator. This system does not require operator interpretation of the received signal, though the signal can be displayed on a screen if desired.
The sound created by the air passage on a scuba regulator is in the same frequency band (32 khz) as that of fish when they transfer gas from one bladder to another, rendering the respiratory system sounds unreliable and open to possible error in operator interpretation. Thus, the filter associated with the cardiovascular channel excludes this band (respiratory system sounds) from the cardiovascular sound channel. This system can be used in a pool or body of water as surveillance against accidental or unauthorized intrusion.
There are some systems on the market to detect objects falling into a swimming pool but they work on motion and a splash and subsequent wave must be present for the alarm to be triggered.
The acoustic signature system of this invention will work without splash, wave, or any form of mechanical movement. The ROM could be programmed for an animal (e.g., dog, cat, etc.) but an inanimate subject will not trigger it (e.g., rock, corpse). However, an unconscious human would be detected.